chore(auth): redesign sign-in and sign-up pages with panel layout

Rebuild the auth pages around a shared AuthPageLayout card with a
three-tier guidance hierarchy: the form (or provider buttons) on top,
a centered switch sentence below it, and a quiet explore band anchored
to the card foot on public instances.

- add AuthPageLayout (brand row, chip, empty state, link prompt,
  explore band gated by instance URL with hideExplore opt-out)
- extract CredentialFields shared by sign-in and sign-up forms
- extract IdentityProviderButtons; fetch the provider list via a
  cached TanStack Query hook with an enabled flag
- cover every instance config: SSO-only, password-only, registrations
  closed, private instance, nothing enabled, first-run setup, admin
- promote /auth/signup, /auth/admin, /auth/callback to ROUTES and add
  appendSearchParams for param-preserving auth links
- move the explore link out of AuthFooter (selectors only now)
- refresh en and zh-Hans auth strings; drop dead keys

web/src/components/AuthPageLayout.tsx

@@ -0,0 +1,90 @@
+import { ArrowRightIcon, CompassIcon } from "lucide-react";
+import { Link } from "react-router-dom";
+import { useInstance } from "@/contexts/InstanceContext";
+import { ROUTES } from "@/router/routes";
+import { useTranslate } from "@/utils/i18n";
+import AuthFooter from "./AuthFooter";
+
+interface Props {
+  chip?: React.ReactNode;
+  title: string;
+  subtitle?: string;
+  // Hide the explore band on pages that shouldn't offer an exit (e.g. first-run setup).
+  hideExplore?: boolean;
+  children: React.ReactNode;
+}
+
+export const AuthChip = ({ children }: { children: React.ReactNode }) => (
+  <span className="inline-flex w-fit items-center gap-1.5 rounded-full border border-border bg-accent/50 px-2.5 py-0.5 text-[10px] font-semibold uppercase tracking-widest text-muted-foreground">
+    {children}
+  </span>
+);
+
+// Centered icon + title + description block for states where a form cannot be shown.
+export const AuthEmptyState = ({
+  icon,
+  title,
+  description,
+  children,
+}: {
+  icon: React.ReactNode;
+  title: string;
+  description: string;
+  children?: React.ReactNode;
+}) => (
+  <div className="flex flex-col items-center py-2 text-center">
+    <div className="mb-3 flex h-11 w-11 items-center justify-center rounded-full bg-accent text-muted-foreground">{icon}</div>
+    <p className="text-sm font-medium text-foreground">{title}</p>
+    <p className="mt-1 text-sm text-muted-foreground">{description}</p>
+    {children}
+  </div>
+);
+
+// "Already have an account? Sign in" style prompt for hopping between auth pages.
+export const AuthLinkPrompt = ({ prompt, to, label }: { prompt: string; to: string; label: string }) => (
+  <p className="mt-5 text-center text-sm text-muted-foreground">
+    {prompt}{" "}
+    <Link to={to} className="text-primary hover:underline" viewTransition>
+      {label}
+    </Link>
+  </p>
+);
+
+const AuthPageLayout = ({ chip, title, subtitle, hideExplore, children }: Props) => {
+  const t = useTranslate();
+  const { generalSetting, profile } = useInstance();
+  const showExplore = Boolean(profile.instanceUrl) && !hideExplore;
+
+  return (
+    <div className="min-h-svh w-full flex flex-col items-center px-4 py-4 sm:py-8">
+      <div className="w-full grow flex flex-col justify-center items-center">
+        <div className="w-90 max-w-full rounded-xl border border-border bg-card p-7 shadow-sm">
+          <div className="mb-6 flex items-center gap-2">
+            <img className="h-6 w-auto rounded-full" src={generalSetting.customProfile?.logoUrl || "/logo.webp"} alt="" />
+            <span className="text-sm font-semibold text-foreground">{generalSetting.customProfile?.title || "Memos"}</span>
+          </div>
+          {chip && <div className="mb-2">{chip}</div>}
+          <h1 className="text-lg font-semibold tracking-tight text-foreground">{title}</h1>
+          {subtitle && <p className="mt-1 text-sm text-muted-foreground">{subtitle}</p>}
+          <div className="mt-6 w-full">{children}</div>
+          {showExplore && (
+            <div className="-mx-7 -mb-7 mt-6 rounded-b-xl border-t border-border bg-background/60">
+              <Link
+                to={ROUTES.EXPLORE}
+                className="group flex items-center justify-center gap-2 px-7 py-3 text-[13px] text-muted-foreground transition-colors hover:text-foreground"
+                viewTransition
+              >
+                <CompassIcon className="h-3.5 w-3.5" />
+                {t("auth.explore-public-memos")}
+                <ArrowRightIcon className="-ml-1 h-3.5 w-3.5 opacity-0 transition-all group-hover:ml-0 group-hover:opacity-100" />
+              </Link>
+            </div>
+          )}
+        </div>
+      </div>
+      <AuthFooter />
+    </div>
+  );
+};
+
+export default AuthPageLayout;

web/src/components/CredentialFields.tsx

@@ -0,0 +1,55 @@
+import { Input } from "@/components/ui/input";
+import { Label } from "@/components/ui/label";
+import { useTranslate } from "@/utils/i18n";
+
+interface Props {
+  idPrefix: string;
+  username: string;
+  password: string;
+  passwordAutoComplete: "current-password" | "new-password";
+  readOnly?: boolean;
+  onUsernameChange: (username: string) => void;
+  onPasswordChange: (password: string) => void;
+}
+
+// Username + password field pair shared by the sign-in and sign-up forms.
+const CredentialFields = ({ idPrefix, username, password, passwordAutoComplete, readOnly, onUsernameChange, onPasswordChange }: Props) => {
+  const t = useTranslate();
+
+  return (
+    <>
+      <div className="flex flex-col gap-1.5">
+        <Label htmlFor={`${idPrefix}-username`}>{t("common.username")}</Label>
+        <Input
+          id={`${idPrefix}-username`}
+          type="text"
+          readOnly={readOnly}
+          placeholder={t("common.username")}
+          value={username}
+          autoComplete="username"
+          autoCapitalize="off"
+          spellCheck={false}
+          onChange={(e) => onUsernameChange(e.target.value)}
+          required
+        />
+      </div>
+      <div className="flex flex-col gap-1.5">
+        <Label htmlFor={`${idPrefix}-password`}>{t("common.password")}</Label>
+        <Input
+          id={`${idPrefix}-password`}
+          type="password"
+          readOnly={readOnly}
+          placeholder={t("common.password")}
+          value={password}
+          autoComplete={passwordAutoComplete}
+          autoCapitalize="off"
+          spellCheck={false}
+          onChange={(e) => onPasswordChange(e.target.value)}
+          required
+        />
+      </div>
+    </>
+  );
+};
+
+export default CredentialFields;

web/src/components/IdentityProviderButtons.tsx

@@ -0,0 +1,67 @@
+import { toast } from "react-hot-toast";
+import { Button } from "@/components/ui/button";
+import { absolutifyLink } from "@/lib/browser";
+import { handleError } from "@/lib/error";
+import { ROUTES } from "@/router/routes";
+import { IdentityProvider, IdentityProvider_Type } from "@/types/proto/api/v1/idp_service_pb";
+import { useTranslate } from "@/utils/i18n";
+import { storeOAuthState } from "@/utils/oauth";
+
+interface Props {
+  identityProviderList: IdentityProvider[];
+  redirectTarget?: string;
+}
+
+const IdentityProviderButtons = ({ identityProviderList, redirectTarget }: Props) => {
+  const t = useTranslate();
+
+  const handleSignInWithIdentityProvider = async (identityProvider: IdentityProvider) => {
+    if (identityProvider.type === IdentityProvider_Type.OAUTH2) {
+      const redirectUri = absolutifyLink(ROUTES.AUTH_CALLBACK);
+      const oauth2Config = identityProvider.config?.config?.case === "oauth2Config" ? identityProvider.config.config.value : undefined;
+      if (!oauth2Config) {
+        toast.error("Identity provider configuration is invalid.");
+        return;
+      }
+
+      try {
+        // Generate and store secure state parameter with CSRF protection
+        // Also generate PKCE parameters (code_challenge) for enhanced security if available
+        const { state, codeChallenge } = await storeOAuthState(identityProvider.name, "signin", redirectTarget);
+
+        // Build OAuth authorization URL with secure state
+        // Include PKCE if available (requires HTTPS/localhost for crypto.subtle)
+        // Using S256 (SHA-256) as the code_challenge_method per RFC 7636
+        let authUrl = `${oauth2Config.authUrl}?client_id=${
+          oauth2Config.clientId
+        }&redirect_uri=${encodeURIComponent(redirectUri)}&state=${state}&response_type=code&scope=${encodeURIComponent(
+          oauth2Config.scopes.join(" "),
+        )}`;
+
+        // Add PKCE parameters if available
+        if (codeChallenge) {
+          authUrl += `&code_challenge=${codeChallenge}&code_challenge_method=S256`;
+        }
+
+        window.location.href = authUrl;
+      } catch (error) {
+        handleError(error, toast.error, {
+          context: "Failed to initiate OAuth flow",
+          fallbackMessage: "Failed to initiate sign-in. Please try again.",
+        });
+      }
+    }
+  };
+
+  return (
+    <div className="flex w-full flex-col gap-2">
+      {identityProviderList.map((identityProvider) => (
+        <Button key={identityProvider.name} variant="outline" onClick={() => handleSignInWithIdentityProvider(identityProvider)}>
+          {t("auth.continue-with", { provider: identityProvider.title })}
+        </Button>
+      ))}
+    </div>
+  );
+};
+
+export default IdentityProviderButtons;

web/src/components/PasswordSignInForm.tsx

@@ -3,8 +3,8 @@ import { LoaderIcon } from "lucide-react";
 import { useState } from "react";
 import { toast } from "react-hot-toast";
 import { setAccessToken } from "@/auth-state";
+import CredentialFields from "@/components/CredentialFields";
 import { Button } from "@/components/ui/button";
-import { Input } from "@/components/ui/input";
 import { authServiceClient } from "@/connect";
 import { useAuth } from "@/contexts/AuthContext";
 import useLoading from "@/hooks/useLoading";
@@ -25,22 +25,9 @@ function PasswordSignInForm({ redirectPath }: PasswordSignInFormProps) {
   const [username, setUsername] = useState("");
   const [password, setPassword] = useState("");
 
-  const handleUsernameInputChanged = (e: React.ChangeEvent<HTMLInputElement>) => {
-    const text = e.target.value as string;
-    setUsername(text);
-  };
-
-  const handlePasswordInputChanged = (e: React.ChangeEvent<HTMLInputElement>) => {
-    const text = e.target.value as string;
-    setPassword(text);
-  };
-
-  const handleFormSubmit = (e: React.FormEvent<HTMLFormElement>) => {
+  const handleFormSubmit = async (e: React.FormEvent<HTMLFormElement>) => {
     e.preventDefault();
-    handleSignInButtonClick();
-  };
 
-  const handleSignInButtonClick = async () => {
     if (username === "" || password === "") {
       return;
     }
@@ -72,45 +59,20 @@ function PasswordSignInForm({ redirectPath }: PasswordSignInFormProps) {
   };
 
   return (
-    <form className="w-full mt-2" onSubmit={handleFormSubmit}>
-      <div className="flex flex-col justify-start items-start w-full gap-4">
-        <div className="w-full flex flex-col justify-start items-start">
-          <span className="leading-8 text-muted-foreground">{t("common.username")}</span>
-          <Input
-            className="w-full bg-background h-10"
-            type="text"
-            readOnly={actionBtnLoadingState.isLoading}
-            placeholder={t("common.username")}
-            value={username}
-            autoComplete="username"
-            autoCapitalize="off"
-            spellCheck={false}
-            onChange={handleUsernameInputChanged}
-            required
-          />
-        </div>
-        <div className="w-full flex flex-col justify-start items-start">
-          <span className="leading-8 text-muted-foreground">{t("common.password")}</span>
-          <Input
-            className="w-full bg-background h-10"
-            type="password"
-            readOnly={actionBtnLoadingState.isLoading}
-            placeholder={t("common.password")}
-            value={password}
-            autoComplete="current-password"
-            autoCapitalize="off"
-            spellCheck={false}
-            onChange={handlePasswordInputChanged}
-            required
-          />
-        </div>
-      </div>
-      <div className="flex flex-row justify-end items-center w-full mt-6">
-        <Button type="submit" className="w-full h-10" disabled={actionBtnLoadingState.isLoading} onClick={handleSignInButtonClick}>
-          {t("common.sign-in")}
-          {actionBtnLoadingState.isLoading && <LoaderIcon className="w-5 h-auto ml-2 animate-spin opacity-60" />}
-        </Button>
-      </div>
+    <form className="flex w-full flex-col gap-4" onSubmit={handleFormSubmit}>
+      <CredentialFields
+        idPrefix="signin"
+        username={username}
+        password={password}
+        passwordAutoComplete="current-password"
+        readOnly={actionBtnLoadingState.isLoading}
+        onUsernameChange={setUsername}
+        onPasswordChange={setPassword}
+      />
+      <Button type="submit" disabled={actionBtnLoadingState.isLoading}>
+        {t("common.sign-in")}
+        {actionBtnLoadingState.isLoading && <LoaderIcon className="ml-1 h-4 w-auto animate-spin opacity-60" />}
+      </Button>
     </form>
   );
 }

web/src/hooks/useIdentityProviderQueries.ts

@@ -0,0 +1,23 @@
+import { useQuery } from "@tanstack/react-query";
+import { identityProviderServiceClient } from "@/connect";
+import { IdentityProvider } from "@/types/proto/api/v1/idp_service_pb";
+
+// Query keys factory
+export const identityProviderKeys = {
+  all: ["identityProviders"] as const,
+  list: () => [...identityProviderKeys.all, "list"] as const,
+};
+
+const EMPTY_LIST: IdentityProvider[] = [];
+
+// Hook to fetch the configured identity providers. Pass `enabled: false` on
+// pages/branches that never render provider buttons to skip the request.
+export function useIdentityProviderList(enabled = true): IdentityProvider[] {
+  const { data } = useQuery({
+    queryKey: identityProviderKeys.list(),
+    queryFn: async () => (await identityProviderServiceClient.listIdentityProviders({})).identityProviders,
+    staleTime: 60_000,
+    enabled,
+  });
+  return data ?? EMPTY_LIST;
+}

web/src/locales/en.json

@@ -8,13 +8,30 @@
     "official-website": "Official Website"
   },
   "auth": {
+    "admin-sign-in": "Administrator sign-in",
+    "admin-sign-in-tip": "Password sign-in stays available for administrators.",
+    "back-to-sign-in": "Back to sign in",
+    "continue-with": "Continue with {{provider}}",
+    "create-admin-account": "Create admin account",
     "create-your-account": "Create your account",
-    "host-tip": "You are registering as the Site Host.",
+    "explore-public-memos": "Explore public memos on this instance",
+    "first-run": "First run",
     "new-password": "New password",
     "protected-memo-notice": "This memo is not public. Sign in to continue.",
     "repeat-new-password": "Repeat the new password",
+    "setup-description": "Create the administrator account for this instance.",
+    "setup-note": "This account owns instance settings, members, and identity providers.",
+    "setup-title": "Set up your instance",
     "sign-in-tip": "Already have an account?",
-    "sign-up-tip": "Don't have an account yet?"
+    "sign-up-tip": "Don't have an account yet?",
+    "signin-unavailable-description": "Password sign-in is turned off and no identity providers are configured. Ask your administrator to enable a sign-in method.",
+    "signin-unavailable-title": "Sign-in is unavailable",
+    "signup-unavailable-description": "Password accounts are turned off and no identity providers are configured. Ask your administrator for access.",
+    "signup-unavailable-title": "Sign-up is unavailable",
+    "signups-closed-description": "New accounts are disabled on this instance. Contact your administrator if you need access.",
+    "signups-closed-title": "Sign-ups are closed",
+    "sso-signup-tip": "Sign in with a provider below to create your account.",
+    "welcome-back": "Welcome back."
   },
   "demo": {
     "banner-description": "Changes are temporary and may be reset.",
@@ -137,7 +154,6 @@
     "shortcut-filter": "Shortcut filter",
     "shortcuts": "Shortcuts",
     "sign-in": "Sign in",
-    "sign-in-with": "Sign in with {{provider}}",
     "sign-out": "Sign out",
     "sign-up": "Sign up",
     "statistics": "Statistics",

web/src/locales/zh-Hans.json

@@ -8,13 +8,30 @@
     "media": "媒体"
   },
   "auth": {
+    "admin-sign-in": "管理员登录",
+    "admin-sign-in-tip": "管理员始终可以使用密码登录。",
+    "back-to-sign-in": "返回登录",
+    "continue-with": "使用 {{provider}} 继续",
+    "create-admin-account": "创建管理员账号",
     "create-your-account": "创建您的账户",
-    "host-tip": "您正在注册为站点管理员。",
+    "explore-public-memos": "浏览此实例上的公开 Memo",
+    "first-run": "首次运行",
     "new-password": "新密码",
     "protected-memo-notice": "此备忘录不是公开的。请先登录后继续。",
     "repeat-new-password": "重复新密码",
+    "setup-description": "为此实例创建管理员账号。",
+    "setup-note": "该账号拥有实例设置、成员与身份提供商的管理权限。",
+    "setup-title": "初始化实例",
     "sign-in-tip": "已有账户？",
-    "sign-up-tip": "还没有账户？"
+    "sign-up-tip": "还没有账户？",
+    "signin-unavailable-description": "密码登录已关闭，且未配置身份提供商。请联系管理员启用登录方式。",
+    "signin-unavailable-title": "无法登录",
+    "signup-unavailable-description": "密码账号已关闭，且未配置身份提供商。如需访问，请联系管理员。",
+    "signup-unavailable-title": "无法注册",
+    "signups-closed-description": "此实例已禁用新账号注册。如需访问，请联系管理员。",
+    "signups-closed-title": "注册已关闭",
+    "sso-signup-tip": "使用以下登录方式即可创建账号。",
+    "welcome-back": "欢迎回来。"
   },
   "demo": {
     "banner-description": "这里的改动是临时的，可能会被重置。",
@@ -105,7 +122,6 @@
     "shortcut-filter": "捷径过滤器",
     "shortcuts": "捷径",
     "sign-in": "登录",
-    "sign-in-with": "使用 {{provider}} 登录",
     "sign-out": "退出登录",
     "sign-up": "注册",
     "statistics": "统计",

web/src/pages/AdminSignIn.tsx

@@ -1,22 +1,32 @@
-import AuthFooter from "@/components/AuthFooter";
+import { ArrowLeftIcon, ShieldCheckIcon } from "lucide-react";
+import { Link } from "react-router-dom";
+import AuthPageLayout, { AuthChip } from "@/components/AuthPageLayout";
 import PasswordSignInForm from "@/components/PasswordSignInForm";
-import { useInstance } from "@/contexts/InstanceContext";
+import { ROUTES } from "@/router/routes";
+import { useTranslate } from "@/utils/i18n";
 
 const AdminSignIn = () => {
-  const { generalSetting: instanceGeneralSetting } = useInstance();
+  const t = useTranslate();
 
   return (
-    <div className="py-4 sm:py-8 w-80 max-w-full min-h-svh mx-auto flex flex-col justify-start items-center">
-      <div className="w-full py-4 grow flex flex-col justify-center items-center">
-        <div className="w-full flex flex-row justify-center items-center mb-6">
-          <img className="h-14 w-auto rounded-full shadow" src={instanceGeneralSetting.customProfile?.logoUrl || "/logo.webp"} alt="" />
-          <p className="ml-2 text-5xl text-foreground opacity-80">{instanceGeneralSetting.customProfile?.title || "Memos"}</p>
-        </div>
-        <p className="w-full text-xl font-medium text-muted-foreground">Sign in with admin accounts</p>
-        <PasswordSignInForm />
-      </div>
-      <AuthFooter />
-    </div>
+    <AuthPageLayout
+      chip={
+        <AuthChip>
+          <ShieldCheckIcon className="h-3 w-3" />
+          {t("common.admin")}
+        </AuthChip>
+      }
+      title={t("auth.admin-sign-in")}
+      subtitle={t("auth.admin-sign-in-tip")}
+    >
+      <PasswordSignInForm />
+      <p className="mt-5 text-center text-sm">
+        <Link to={ROUTES.AUTH} className="inline-flex items-center gap-1 text-primary hover:underline" viewTransition>
+          <ArrowLeftIcon className="h-3.5 w-3.5" />
+          {t("auth.back-to-sign-in")}
+        </Link>
+      </p>
+    </AuthPageLayout>
   );
 };
 

web/src/pages/SignIn.tsx

@@ -1,122 +1,62 @@
-import { useEffect, useState } from "react";
-import { toast } from "react-hot-toast";
+import { ArrowRightIcon, LockIcon } from "lucide-react";
 import { Link, useSearchParams } from "react-router-dom";
-import AuthFooter from "@/components/AuthFooter";
+import AuthPageLayout, { AuthEmptyState, AuthLinkPrompt } from "@/components/AuthPageLayout";
+import IdentityProviderButtons from "@/components/IdentityProviderButtons";
 import PasswordSignInForm from "@/components/PasswordSignInForm";
-import { Button } from "@/components/ui/button";
 import { Separator } from "@/components/ui/separator";
-import { identityProviderServiceClient } from "@/connect";
 import { useInstance } from "@/contexts/InstanceContext";
-import { absolutifyLink } from "@/lib/browser";
-import { handleError } from "@/lib/error";
+import { useIdentityProviderList } from "@/hooks/useIdentityProviderQueries";
 import { ROUTES } from "@/router/routes";
-import { IdentityProvider, IdentityProvider_Type } from "@/types/proto/api/v1/idp_service_pb";
-import { AUTH_REDIRECT_PARAM, getSafeRedirectPath } from "@/utils/auth-redirect";
+import { AUTH_REDIRECT_PARAM, appendSearchParams, getSafeRedirectPath } from "@/utils/auth-redirect";
 import { useTranslate } from "@/utils/i18n";
-import { storeOAuthState } from "@/utils/oauth";
 
 const SignIn = () => {
   const t = useTranslate();
-  const [identityProviderList, setIdentityProviderList] = useState<IdentityProvider[]>([]);
   const { generalSetting: instanceGeneralSetting } = useInstance();
   const [searchParams] = useSearchParams();
+  const identityProviderList = useIdentityProviderList();
   const redirectTarget = getSafeRedirectPath(searchParams.get(AUTH_REDIRECT_PARAM));
-  const signUpPath = searchParams.toString() ? `${ROUTES.AUTH}/signup?${searchParams.toString()}` : `${ROUTES.AUTH}/signup`;
+  const signUpPath = appendSearchParams(ROUTES.AUTH_SIGNUP, searchParams);
 
-  // Prepare identity provider list.
-  useEffect(() => {
-    const fetchIdentityProviderList = async () => {
-      const { identityProviders } = await identityProviderServiceClient.listIdentityProviders({});
-      setIdentityProviderList(identityProviders);
-    };
-    fetchIdentityProviderList();
-  }, []);
+  const passwordAuthAllowed = !instanceGeneralSetting.disallowPasswordAuth;
+  const hasIdentityProviders = identityProviderList.length > 0;
 
-  const handleSignInWithIdentityProvider = async (identityProvider: IdentityProvider) => {
-    if (identityProvider.type === IdentityProvider_Type.OAUTH2) {
-      const redirectUri = absolutifyLink("/auth/callback");
-      const oauth2Config = identityProvider.config?.config?.case === "oauth2Config" ? identityProvider.config.config.value : undefined;
-      if (!oauth2Config) {
-        toast.error("Identity provider configuration is invalid.");
-        return;
-      }
-
-      try {
-        // Generate and store secure state parameter with CSRF protection
-        // Also generate PKCE parameters (code_challenge) for enhanced security if available
-        const { state, codeChallenge } = await storeOAuthState(identityProvider.name, "signin", redirectTarget);
-
-        // Build OAuth authorization URL with secure state
-        // Include PKCE if available (requires HTTPS/localhost for crypto.subtle)
-        // Using S256 (SHA-256) as the code_challenge_method per RFC 7636
-        let authUrl = `${oauth2Config.authUrl}?client_id=${
-          oauth2Config.clientId
-        }&redirect_uri=${encodeURIComponent(redirectUri)}&state=${state}&response_type=code&scope=${encodeURIComponent(
-          oauth2Config.scopes.join(" "),
-        )}`;
-
-        // Add PKCE parameters if available
-        if (codeChallenge) {
-          authUrl += `&code_challenge=${codeChallenge}&code_challenge_method=S256`;
-        }
-
-        window.location.href = authUrl;
-      } catch (error) {
-        handleError(error, toast.error, {
-          context: "Failed to initiate OAuth flow",
-          fallbackMessage: "Failed to initiate sign-in. Please try again.",
-        });
-      }
-    }
-  };
+  const subtitle = passwordAuthAllowed || hasIdentityProviders ? t("auth.welcome-back") : undefined;
 
   return (
-    <div className="py-4 sm:py-8 w-80 max-w-full min-h-svh mx-auto flex flex-col justify-start items-center">
-      <div className="w-full py-4 grow flex flex-col justify-center items-center">
-        <div className="w-full flex flex-row justify-center items-center mb-6">
-          <img className="h-14 w-auto rounded-full shadow" src={instanceGeneralSetting.customProfile?.logoUrl || "/logo.webp"} alt="" />
-          <p className="ml-2 text-5xl text-foreground opacity-80">{instanceGeneralSetting.customProfile?.title || "Memos"}</p>
-        </div>
-        {!instanceGeneralSetting.disallowPasswordAuth ? (
-          <PasswordSignInForm redirectPath={redirectTarget} />
-        ) : (
-          identityProviderList.length === 0 && <p className="w-full text-2xl mt-2 text-muted-foreground">Password auth is not allowed.</p>
-        )}
-        {!instanceGeneralSetting.disallowUserRegistration && !instanceGeneralSetting.disallowPasswordAuth && (
-          <p className="w-full mt-4 text-sm">
-            <span className="text-muted-foreground">{t("auth.sign-up-tip")}</span>
-            <Link to={signUpPath} className="cursor-pointer ml-2 text-primary hover:underline" viewTransition>
-              {t("common.sign-up")}
-            </Link>
-          </p>
-        )}
-        {identityProviderList.length > 0 && (
-          <>
-            {!instanceGeneralSetting.disallowPasswordAuth && (
-              <div className="relative my-4 w-full">
+    <AuthPageLayout title={t("common.sign-in")} subtitle={subtitle}>
+      {passwordAuthAllowed || hasIdentityProviders ? (
+        <>
+          {hasIdentityProviders && <IdentityProviderButtons identityProviderList={identityProviderList} redirectTarget={redirectTarget} />}
+          {hasIdentityProviders && passwordAuthAllowed && (
+            <div className="my-4 flex items-center gap-3 text-xs uppercase tracking-wider text-muted-foreground">
+              <div className="flex-1">
+                <Separator />
+              </div>
+              {t("common.or")}
+              <div className="flex-1">
                 <Separator />
-                <div className="absolute inset-0 flex items-center justify-center">
-                  <span className="bg-background px-2 text-xs text-muted-foreground">{t("common.or")}</span>
-                </div>
               </div>
-            )}
-            <div className="w-full flex flex-col space-y-2">
-              {identityProviderList.map((identityProvider) => (
-                <Button
-                  className="bg-background w-full"
-                  key={identityProvider.name}
-                  variant="outline"
-                  onClick={() => handleSignInWithIdentityProvider(identityProvider)}
-                >
-                  {t("common.sign-in-with", { provider: identityProvider.title })}
-                </Button>
-              ))}
             </div>
-          </>
-        )}
-      </div>
-      <AuthFooter />
-    </div>
+          )}
+          {passwordAuthAllowed && <PasswordSignInForm redirectPath={redirectTarget} />}
+          {passwordAuthAllowed && !instanceGeneralSetting.disallowUserRegistration && (
+            <AuthLinkPrompt prompt={t("auth.sign-up-tip")} to={signUpPath} label={t("common.sign-up")} />
+          )}
+        </>
+      ) : (
+        <AuthEmptyState
+          icon={<LockIcon className="h-5 w-5" />}
+          title={t("auth.signin-unavailable-title")}
+          description={t("auth.signin-unavailable-description")}
+        >
+          <Link to={ROUTES.AUTH_ADMIN} className="mt-3 inline-flex items-center gap-1 text-sm text-primary hover:underline" viewTransition>
+            {t("auth.admin-sign-in")}
+            <ArrowRightIcon className="h-3.5 w-3.5" />
+          </Link>
+        </AuthEmptyState>
+      )}
+    </AuthPageLayout>
   );
 };
 

web/src/pages/SignUp.tsx

@@ -1,22 +1,24 @@
 import { create } from "@bufbuild/protobuf";
 import { timestampDate } from "@bufbuild/protobuf/wkt";
-import { LoaderIcon } from "lucide-react";
+import { InfoIcon, LoaderIcon, LockIcon, SparklesIcon, UserRoundXIcon } from "lucide-react";
 import { useState } from "react";
 import { toast } from "react-hot-toast";
-import { Link, useSearchParams } from "react-router-dom";
+import { useSearchParams } from "react-router-dom";
 import { setAccessToken } from "@/auth-state";
-import AuthFooter from "@/components/AuthFooter";
+import AuthPageLayout, { AuthChip, AuthEmptyState, AuthLinkPrompt } from "@/components/AuthPageLayout";
+import CredentialFields from "@/components/CredentialFields";
+import IdentityProviderButtons from "@/components/IdentityProviderButtons";
 import { Button } from "@/components/ui/button";
-import { Input } from "@/components/ui/input";
 import { authServiceClient, userServiceClient } from "@/connect";
 import { useAuth } from "@/contexts/AuthContext";
 import { useInstance } from "@/contexts/InstanceContext";
+import { useIdentityProviderList } from "@/hooks/useIdentityProviderQueries";
 import useLoading from "@/hooks/useLoading";
 import useNavigateTo from "@/hooks/useNavigateTo";
 import { handleError } from "@/lib/error";
 import { ROUTES } from "@/router/routes";
 import { User_Role, UserSchema } from "@/types/proto/api/v1/user_service_pb";
-import { AUTH_REDIRECT_PARAM, getSafeRedirectPath } from "@/utils/auth-redirect";
+import { AUTH_REDIRECT_PARAM, appendSearchParams, getSafeRedirectPath } from "@/utils/auth-redirect";
 import { useTranslate } from "@/utils/i18n";
 
 const SignUp = () => {
@@ -29,25 +31,18 @@ const SignUp = () => {
   const { generalSetting: instanceGeneralSetting, profile, initialize: initInstance } = useInstance();
   const [searchParams] = useSearchParams();
   const redirectTarget = getSafeRedirectPath(searchParams.get(AUTH_REDIRECT_PARAM));
-  const signInPath = searchParams.toString() ? `${ROUTES.AUTH}?${searchParams.toString()}` : ROUTES.AUTH;
-  const canUsePasswordSignUp = !instanceGeneralSetting.disallowUserRegistration && !instanceGeneralSetting.disallowPasswordAuth;
+  const signInPath = appendSearchParams(ROUTES.AUTH, searchParams);
 
-  const handleUsernameInputChanged = (e: React.ChangeEvent<HTMLInputElement>) => {
-    const text = e.target.value as string;
-    setUsername(text);
-  };
+  const passwordAuthAllowed = !instanceGeneralSetting.disallowPasswordAuth;
+  const registrationOpen = !instanceGeneralSetting.disallowUserRegistration;
+  const needsSetup = profile.needsSetup;
+  // Provider buttons only render on the SSO-provisioned branch below; skip the request elsewhere.
+  const identityProviderList = useIdentityProviderList(!needsSetup && registrationOpen && !passwordAuthAllowed);
+  const hasIdentityProviders = identityProviderList.length > 0;
 
-  const handlePasswordInputChanged = (e: React.ChangeEvent<HTMLInputElement>) => {
-    const text = e.target.value as string;
-    setPassword(text);
-  };
-
-  const handleFormSubmit = (e: React.FormEvent<HTMLFormElement>) => {
+  const handleFormSubmit = async (e: React.FormEvent<HTMLFormElement>) => {
     e.preventDefault();
-    handleSignUpButtonClick();
-  };
 
-  const handleSignUpButtonClick = async () => {
     if (username === "" || password === "") {
       return;
     }
@@ -87,75 +82,87 @@ const SignUp = () => {
     actionBtnLoadingState.setFinish();
   };
 
-  return (
-    <div className="py-4 sm:py-8 w-80 max-w-full min-h-svh mx-auto flex flex-col justify-start items-center">
-      <div className="w-full py-4 grow flex flex-col justify-center items-center">
-        <div className="w-full flex flex-row justify-center items-center mb-6">
-          <img className="h-14 w-auto rounded-full shadow" src={instanceGeneralSetting.customProfile?.logoUrl || "/logo.webp"} alt="" />
-          <p className="ml-2 text-5xl text-foreground opacity-80">{instanceGeneralSetting.customProfile?.title || "Memos"}</p>
+  const signUpForm = (
+    <form className="flex w-full flex-col gap-4" onSubmit={handleFormSubmit}>
+      <CredentialFields
+        idPrefix="signup"
+        username={username}
+        password={password}
+        passwordAutoComplete="new-password"
+        readOnly={actionBtnLoadingState.isLoading}
+        onUsernameChange={setUsername}
+        onPasswordChange={setPassword}
+      />
+      <Button type="submit" disabled={actionBtnLoadingState.isLoading}>
+        {needsSetup ? t("auth.create-admin-account") : t("common.sign-up")}
+        {actionBtnLoadingState.isLoading && <LoaderIcon className="ml-1 h-4 w-auto animate-spin opacity-60" />}
+      </Button>
+    </form>
+  );
+
+  const signInPrompt = <AuthLinkPrompt prompt={t("auth.sign-in-tip")} to={signInPath} label={t("common.sign-in")} />;
+
+  // First run: create the instance owner account.
+  if (needsSetup) {
+    return (
+      <AuthPageLayout
+        chip={
+          <AuthChip>
+            <SparklesIcon className="h-3 w-3" />
+            {t("auth.first-run")}
+          </AuthChip>
+        }
+        title={t("auth.setup-title")}
+        subtitle={t("auth.setup-description")}
+        hideExplore
+      >
+        {signUpForm}
+        <div className="mt-4 flex items-start gap-2 rounded-lg border border-border bg-accent/50 px-3 py-2 text-[13px] leading-relaxed text-muted-foreground">
+          <InfoIcon className="mt-0.5 h-3.5 w-3.5 shrink-0" />
+          {t("auth.setup-note")}
         </div>
-        {canUsePasswordSignUp ? (
-          <>
-            <p className="w-full text-2xl mt-2 text-muted-foreground">{t("auth.create-your-account")}</p>
-            <form className="w-full mt-2" onSubmit={handleFormSubmit}>
-              <div className="flex flex-col justify-start items-start w-full gap-4">
-                <div className="w-full flex flex-col justify-start items-start">
-                  <span className="leading-8 text-muted-foreground">{t("common.username")}</span>
-                  <Input
-                    className="w-full bg-background h-10"
-                    type="text"
-                    readOnly={actionBtnLoadingState.isLoading}
-                    placeholder={t("common.username")}
-                    value={username}
-                    autoComplete="username"
-                    autoCapitalize="off"
-                    spellCheck={false}
-                    onChange={handleUsernameInputChanged}
-                    required
-                  />
-                </div>
-                <div className="w-full flex flex-col justify-start items-start">
-                  <span className="leading-8 text-muted-foreground">{t("common.password")}</span>
-                  <Input
-                    className="w-full bg-background h-10"
-                    type="password"
-                    readOnly={actionBtnLoadingState.isLoading}
-                    placeholder={t("common.password")}
-                    value={password}
-                    autoComplete="new-password"
-                    autoCapitalize="off"
-                    spellCheck={false}
-                    onChange={handlePasswordInputChanged}
-                    required
-                  />
-                </div>
-              </div>
-              <div className="flex flex-row justify-end items-center w-full mt-6">
-                <Button type="submit" className="w-full h-10" disabled={actionBtnLoadingState.isLoading} onClick={handleSignUpButtonClick}>
-                  {t("common.sign-up")}
-                  {actionBtnLoadingState.isLoading && <LoaderIcon className="w-5 h-auto ml-2 animate-spin opacity-60" />}
-                </Button>
-              </div>
-            </form>
-          </>
-        ) : instanceGeneralSetting.disallowPasswordAuth ? (
-          <p className="w-full text-2xl mt-2 text-muted-foreground">Password sign up is not allowed.</p>
+      </AuthPageLayout>
+    );
+  }
+
+  // Registration closed.
+  if (!registrationOpen) {
+    return (
+      <AuthPageLayout title={t("auth.create-your-account")}>
+        <AuthEmptyState
+          icon={<UserRoundXIcon className="h-5 w-5" />}
+          title={t("auth.signups-closed-title")}
+          description={t("auth.signups-closed-description")}
+        />
+        {signInPrompt}
+      </AuthPageLayout>
+    );
+  }
+
+  // Password sign-up disallowed: accounts come from the identity provider.
+  if (!passwordAuthAllowed) {
+    return (
+      <AuthPageLayout title={t("auth.create-your-account")} subtitle={hasIdentityProviders ? t("auth.sso-signup-tip") : undefined}>
+        {hasIdentityProviders ? (
+          <IdentityProviderButtons identityProviderList={identityProviderList} redirectTarget={redirectTarget} />
         ) : (
-          <p className="w-full text-2xl mt-2 text-muted-foreground">Sign up is not allowed.</p>
+          <AuthEmptyState
+            icon={<LockIcon className="h-5 w-5" />}
+            title={t("auth.signup-unavailable-title")}
+            description={t("auth.signup-unavailable-description")}
+          />
         )}
-        {profile.needsSetup ? (
-          <p className="w-full mt-4 text-sm font-medium text-muted-foreground">{t("auth.host-tip")}</p>
-        ) : (
-          <p className="w-full mt-4 text-sm">
-            <span className="text-muted-foreground">{t("auth.sign-in-tip")}</span>
-            <Link to={signInPath} className="cursor-pointer ml-2 text-primary hover:underline" viewTransition>
-              {t("common.sign-in")}
-            </Link>
-          </p>
-        )}
-      </div>
-      <AuthFooter />
-    </div>
+        {signInPrompt}
+      </AuthPageLayout>
+    );
+  }
+
+  // Open registration.
+  return (
+    <AuthPageLayout title={t("auth.create-your-account")}>
+      {signUpForm}
+      {signInPrompt}
+    </AuthPageLayout>
   );
 };
 

web/src/router/routes.ts

@@ -8,6 +8,9 @@ export const ROUTES = {
   SETTING: "/setting",
   EXPLORE: "/explore",
   AUTH: "/auth",
+  AUTH_SIGNUP: "/auth/signup",
+  AUTH_ADMIN: "/auth/admin",
+  AUTH_CALLBACK: "/auth/callback",
   SHARED_MEMO: "/memos/shares",
 } as const;
 

web/src/utils/auth-redirect.ts

@@ -9,6 +9,7 @@ export {
   AUTH_REASON_PARAM,
   AUTH_REASON_PROTECTED_MEMO,
   AUTH_REDIRECT_PARAM,
+  appendSearchParams,
   buildAuthRoute,
   getSafeRedirectPath,
   isPublicRoute,

web/src/utils/redirect-safety.ts

@@ -87,3 +87,12 @@ export function shouldGatePrivateInstance(params: { isPrivateInstance: boolean;
   }
   return !pathname.startsWith(`${ROUTES.SHARED_MEMO}/`);
 }
+
+/**
+ * Appends the given search params to a path, so links between auth pages
+ * (sign-in <-> sign-up) preserve the redirect target and other params.
+ */
+export function appendSearchParams(path: string, searchParams: URLSearchParams): string {
+  const queryString = searchParams.toString();
+  return queryString ? `${path}?${queryString}` : path;
+}

web/tests/auth-page-layout.test.tsx

@@ -0,0 +1,52 @@
+import { render, screen } from "@testing-library/react";
+import { MemoryRouter } from "react-router-dom";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import AuthPageLayout from "@/components/AuthPageLayout";
+
+const instance = vi.hoisted(() => ({ instanceUrl: "" }));
+
+vi.mock("@/contexts/InstanceContext", () => ({
+  useInstance: () => ({ profile: instance, generalSetting: {} }),
+}));
+
+vi.mock("@/utils/i18n", () => ({
+  useTranslate: () => (key: string) => key,
+  loadLocale: vi.fn(),
+}));
+
+vi.mock("@/components/AuthFooter", () => ({ default: () => <div data-testid="auth-footer" /> }));
+
+const renderLayout = (props?: { hideExplore?: boolean }) =>
+  render(
+    <MemoryRouter>
+      <AuthPageLayout title="Sign in" {...props}>
+        <div />
+      </AuthPageLayout>
+    </MemoryRouter>,
+  );
+
+describe("<AuthPageLayout> explore band", () => {
+  beforeEach(() => {
+    instance.instanceUrl = "";
+  });
+
+  it("links to Explore on public instances", () => {
+    instance.instanceUrl = "https://demo.example.com";
+    renderLayout();
+
+    expect(screen.getByRole("link", { name: /auth\.explore-public-memos/ })).toHaveAttribute("href", "/explore");
+  });
+
+  it("omits the band on private instances", () => {
+    renderLayout();
+
+    expect(screen.queryByRole("link", { name: /auth\.explore-public-memos/ })).not.toBeInTheDocument();
+  });
+
+  it("omits the band when hideExplore is set (first-run setup)", () => {
+    instance.instanceUrl = "https://demo.example.com";
+    renderLayout({ hideExplore: true });
+
+    expect(screen.queryByRole("link", { name: /auth\.explore-public-memos/ })).not.toBeInTheDocument();
+  });
+});